Seroprevalence and distribution of arboviral infections among rural Kenyan adults: A cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Arthorpod-borne viruses (arboviruses) cause wide-spread morbidity in sub-Saharan Africa, but little research has documented the burden and distribution of these pathogens.</p> <p>Methods</p> <p>Using a population-based, cross-sectional study design, we administered a detailed questionnaire and used ELISA to test the blood of 1,141 healthy Kenyan adults from three districts for the presence of anti-viral Immunoglobulin G (IgG) antibodies to the following viruses: dengue (DENV), West Nile (WNV), yellow fever (YFV), Chikungunya (CHIKV), and Rift Valley fever (RVFV).</p> <p>Results</p> <p>Of these, 14.4% were positive for DENV, 9.5% were WNV positive, 9.2% were YFV positive, 34.0% were positive for CHIKV and 0.7% were RVFV positive. In total, 46.6% had antibodies to at least one of these arboviruses.</p> <p>Conclusions</p> <p>For all arboviruses, district of residence was strongly associated with seropositivity. Seroprevalence to YFV, DENV and WNV increased with age, while there was no correlation between age and seropositivity for CHIKV, suggesting that much of the seropositivity to CHIKV is due to sporadic epidemics. Paradoxically, literacy was associated with increased seropositivity of CHIKV and DENV.</p

Measuring the burden of arboviral diseases: the spectrum of morbidity and mortality from four prevalent infections

<p>Abstract</p> <p>Background</p> <p>Globally, arthropod-borne virus infections are increasingly common causes of severe febrile disease that can progress to long-term physical or cognitive impairment or result in early death. Because of the large populations at risk, it has been suggested that these outcomes represent a substantial health deficit not captured by current global disease burden assessments.</p> <p>Methods</p> <p>We reviewed newly available data on disease incidence and outcomes to critically evaluate the disease burden (as measured by disability-adjusted life years, or DALYs) caused by yellow fever virus (YFV), Japanese encephalitis virus (JEV), chikungunya virus (CHIKV), and Rift Valley fever virus (RVFV). We searched available literature and official reports on these viruses combined with the terms "outbreak(s)," "complication(s)," "disability," "quality of life," "DALY," and "QALY," focusing on reports since 2000. We screened 210 published studies, with 38 selected for inclusion. Data on average incidence, duration, age at onset, mortality, and severity of acute and chronic outcomes were used to create DALY estimates for 2005, using the approach of the current Global Burden of Disease framework.</p> <p>Results</p> <p>Given the limitations of available data, nondiscounted, unweighted DALYs attributable to YFV, JEV, CHIKV, and RVFV were estimated to fall between 300,000 and 5,000,000 for 2005. YFV was the most prevalent infection of the four viruses evaluated, although a higher proportion of the world's population lives in countries at risk for CHIKV and JEV. Early mortality and long-term, related chronic conditions provided the largest DALY components for each disease. The better known, short-term viral febrile syndromes caused by these viruses contributed relatively lower proportions of the overall DALY scores.</p> <p>Conclusions</p> <p>Limitations in health systems in endemic areas undoubtedly lead to underestimation of arbovirus incidence and related complications. However, improving diagnostics and better understanding of the late secondary results of infection now give a first approximation of the current disease burden from these widespread serious infections. Arbovirus control and prevention remains a high priority, both because of the current disease burden and the significant threat of the re-emergence of these viruses among much larger groups of susceptible populations.</p

Population genomics reveals that an anthropophilic population of Aedes aegypti\textit{Aedes aegypti} mosquitoes in West Africa recently gave rise to American and Asian populations of this major disease vector

$\textbf{BACKGROUND}$: The mosquito $\textit{Aedes aegypti}$ is the main vector of dengue, Zika, chikungunya and yellow fever viruses. This major disease vector is thought to have arisen when the African subspecies $\textit{Ae. aegypti}$ formosus evolved from being zoophilic and living in forest habitats into a form that specialises on humans and resides near human population centres. The resulting domestic subspecies, $\textit{Ae. aegypti aegypti}$, is found throughout the tropics and largely blood-feeds on humans. $\textbf{RESULTS}$: To understand this transition, we have sequenced the exomes of mosquitoes collected from five populations from around the world. We found that $\textit{Ae. aegypti}$ specimens from an urban population in Senegal in West Africa were more closely related to populations in Mexico and Sri Lanka than they were to a nearby forest population. We estimate that the populations in Senegal and Mexico split just a few hundred years ago, and we found no evidence of $\textit{Ae. aegypti aegypti}$ mosquitoes migrating back to Africa from elsewhere in the tropics. The out-of-Africa migration was accompanied by a dramatic reduction in effective population size, resulting in a loss of genetic diversity and rare genetic variants. $\textbf{CONCLUSIONS}$: We conclude that a domestic population of $\textit{Ae. aegypti}$ in Senegal and domestic populations on other continents are more closely related to each other than to other African populations. This suggests that an ancestral population of $\textit{Ae. aegypti }$evolved to become a human specialist in Africa, giving rise to the subspecies $\textit{Ae. aegypti aegypti}$. The descendants of this population are still found in West Africa today, and the rest of the world was colonised when mosquitoes from this population migrated out of Africa. This is the first report of an African population of Ae. aegypti aegypti mosquitoes that is closely related to Asian and American populations. As the two subspecies differ in their ability to vector disease, their existence side by side in West Africa may have important implications for disease transmission.This work was funded by European Research Council grant Drosophila Infection 281668 to FMJ, a KAUST AEA award to FMJ and AP, a Medical Research Council Centenary Award to WJP and a National Institutes of Health Ruth L. Kirschstein National Research Service Award to JC

First record in America of Aedes albopictus naturally infected with dengue virus during the 1995 outbreak at Reynosa, Mexico

Mosquito collections were conducted during a dengue outbreak in Reynosa, Tamaulipas, Mexico, July-December 1995. A total of 6694 adult mosquitoes (four genera and nine species) were captured, of which 2986 (78.3% females and 21.7% males) were Aedes albopictus and 2339 (39.7% females and 60.3% males) were Ae.aegypti. These two species comprised 84.2% of the total collection. Specimens were grouped into pools, nearly 50% of them processed for detection of virus by cythopathic effect in C6-36 and VERO cell cultures and by haemagglutination test. Five pools gave positive haemagglutination reactions and were examined by immunofluorescence using monoclonal antibodies to flavivirus and to dengue virus. One pool of ten Ae.albopictus males was positive for dengue virus: serotypes 2 and 3 were identified by serotype-specific monoclonal antibodies and confirmed by RT-PCR. This is the first report of Ae.albopictus naturally infected with dengue virus in America. Also, it is the very first time Ae.albopictus males have been found infected with dengue virus in the wild